/* 确保按钮默认隐藏，滚动到一定位置后显示 */
.back-to-top {
  position: fixed;
  right: 20px;
  bottom: 20px;
  padding: 10px 15px;
  background: #1890ff;
  color: white;
  border: none;
  border-radius: 4px;
  cursor: pointer;
  opacity: 0;
  transition: opacity 0.3s;
  display: flex;
  align-items: center;
  gap: 8px;
}

.back-to-top.visible {
  opacity: 1;
}

.back-to-top:hover {
  background: #40a9ff;
}

.back-to-top-icon {
  font-size: 16px;
}